#include <iostream>

using namespace std;
const int N = 1010;
int n, m;
int t[N], w[N];
int f[N];
int main()
{
	cin >> m >> n;
	for (int i = 1; i <= n; i++) cin >> t[i] >> w[i];

	for (int i = 1; i <= n; i++)
	{
		for (int j = m; j >= t[i]; j--)
		{
				f[j] = max(f[j], f[j-t[i]] + w[i]);
		}
	}
	cout << f[m] << endl;
	return 0;
}